1. Field of the Invention
The present invention relates to a facsimile apparatus having a control circuit substrate in which noise shielding and ground connections have been effected.
2. Related Background Art
With the rapid spread of facsimiles all over the world in recent years, it is required to be easily cope with different power supplies such as 100 V, 120 V and 230 V and different public lines in various counties. Moreover, it is also desired that parts be easily molded and fabricated in any place as they are locally manufactured all over the world. Further, a facsimile structure easy to perform the maintenance work is also needed.
In addition, the restriction against noise radiated from the apparatus is getting severe day by day. It is also required to prevent the malfunction arising from static electricity applied to the apparatus by the operator, and it is important that the malfunction arising from the static electricity caused by the apparatus itself due to the internal recording action be prevented.
The conventional facsimile apparatus has a construction in which a plurality of molded top covers 32 and bottom covers 33 are mounted on a molded body frame 31 as shown in FIG. 11. In order to assemble such facsimile, a control circuit substrate 34 (including a system control unit and a network control unit) is first attached onto the bottom cover 33, and then there is arranged the body frame 31 on which units and electronic components are assembled so as to drop-in. In the course of this assembling, an input/output terminal 35 for circuits or the like is fixed to the far side (left side in the figure) of the bottom cover 33. Finally, the upper cover 32 and the like are mounted to complete the assembling.
Besides, as a noise shielding means, a conductive coating is applied to the bottom surface of the body frame 31 and the top surface of the bottom cover 33, which are connected through a multiplicity of ground wires 37 to the ground of a power supply source. Further, a shielding metallic plate 38 is disposed between the circuit substrate 34 and the bottom cover 33.
Signal lines extending from the control circuit substrate 34 to sensors, a recording means, and a reading means are previously connected by the respective connectors or the like, and finally while forcing the separate cables in, the body frame 31 is put down to close the cover and the like. As a result, the wires are caught by the working parts to lead to a malfunction such as short-circuiting. Furthermore, when the noise shield is provided under the control circuit substrate 34, the shielding metallic plate 38 is arranged over the bottom cover 33, to consequently present a double structure of the metallic plate and the molded part under the substrate 34, thus leading to the increase in thickness of the entire apparatus, which prevents the miniaturization of the apparatus.
Moreover, as a measure to prevent the radiation noise, a conductive coating is applied to the bottom cover 33, the body frame 31 and the like, but a multiplicity of ground wires must be screwed to the frame to ground the coating. Since the conductive coating has a film thickness of only several 10 .mu.m, it must be grounded at more points as compared to the metallic plate having a thickness of 0.5 to 1.0 mm so as to obtain a noise shielding effect. Also, the conductive coating itself is substantially expensive, which causes an increase in the production costs along with the bundling work of the ground cables as described earlier. Furthermore, signals transmitted from the circuit substrate 34 to an operation panel or a thermal head are switched at high speed, which produces a noise. In the above-mentioned assembling method, the position of the signal wires and the like on the circuit substrate 34 differs according to the assembling step, thus making it very hard to control the prevention of noise occurrence.
In order to compensate the inconveniences described above, there is proposed an apparatus in which the cover members are molded in stead of using metallic plates so as not to cause static electricity. In this case, however, an aperture for connecting the terminals on the circuit substrate 34 must be provided on the side wall of the bottom cover, with result that there must be provided various shapes of apertures for modules or terminal supports which differ depending on the destinations in the world, thus leading to the increase in the production cost due to the manufacture of other bottom covers using expensive dies.
Moreover, a power supply unit 39 is separated from the circuit substrate 34 by the body frame 31, and hence the electrical connection between the power supply unit 39 and the circuit substrate 34 is carried out through an aperture 40 provided on the body frame 31. Ground connections for the power supply unit 39 and the circuit substrate 34 are also conducted through the aperture on the body frame 31 in the same manner.
Here, description will be made of the case where the control circuit substrate 34 is used as the circuit substrate unit with reference to FIG. 11.
In the output section of the power supply unit 39, a power supply connector 41 is fitted to the output circuit of a power supply substrate 39.sub.1, while a control connector 34a is fitted to the control circuit substrate 34.
To electrically connect the power supply unit 39 with the control circuit substrate 34 during the assembly, a first connector 42a located at one end of a connection cord 42 is previously coupled with a power supply connector 41 of the power supply substrate 39.sub.1, a second connector 42b located at another end of the connection cord 42 is inserted into the aperture 40 from a power supply unit receiving section side (the left side in the figure), and then the power supply unit 39 is dropped in the receiving section provided at the end of the apparatus body. And finally the second connector 42b of the connection cord 42 is linked with a control connector 34a of the control circuit substrate 34.
Also, as measures to prevent static electricity and the falling of a thundervolt, a power supply unit frame 39.sub.2 and the control circuit substrate 34 are connected to the ground wire 37 by means of screws respectively, so as to equalize the voltage to ground between the power supply unit 39 and the control circuit substrate 34.
Due to this, the ground wire 37 also must go through the aperture 40 on the body frame 31 to execute the ground connections for a power supply unit frame 31.sub.2 and the control circuit substrate 34. At the time of assembling, one end of the ground wire 37 is previously connected to the power supply unit frame 31.sub.2, whereas the other end of the ground wire 37 is inserted into an aperture 35 from the power supply unit receiving section side (left side in the figure), and then the power supply unit 31 is dropped in the receiving section provided at the end portion of the apparatus body to complete the assembly.
The operations for inserting the connection cord 42 and the ground wire into the aperture are difficult to carry out by an automatic machine, and hence it is to be manually performed. Accordingly, in the case where each unit is automatically assembled by a drop-in method, during the assembly of the power supply unit 39, the automatic assembly has to be temporarily interrupted to perform a manual working. After that, the automatic assembling work is restarted, which leads to the increase in the number of working processes, resulting in an extremely insufficient and time-consuming assembling steps, to consequently bring about a raise in production costs.